1. Field of the Invention
The present invention relates to a high density alloy for an article of manufacture. More specifically, the present invention relates to a high density alloy for an iron golf club.
2. Description of the Related Art
Current materials do not allow for sufficient design flexibility to manipulate the mass properties of certain articles of manufacture such as golf club heads. The density of metallic materials may be manipulated by mixing elemental powders in specific proportions and then pressing and sintering the mixture to form a dense body. However, this process does not necessarily create a metallic alloy since the local composition is quite different from the bulk composition. Further, such a sintering process creates manufacturing difficulties and does not provide sufficient mechanical properties.
Investment casting is a well-known and simple manufacturing process for creating numerous metallic articles such as golf club heads. High density metals such as molybdenum (10.2 grams per cubic centimeter (“g/cm3”)), tantalum (16.6 g/cm3) and tungsten (19.3 g/cm3) cannot be used directly since these high density metals are extremely refractory. Other high density metals such as gold (19.3 g/cm3), silver (10.5 g/cm3) and platinum (21.4 g/cm3) are too expensive for high volume low cost articles, and these high priced metals do not possess the requisite mechanical properties.
Iron (7.86 g/cm3) and nickel (8.90 g/cm3) are not very refractory, have good mechanical properties and are reasonably priced for high volume low cost articles. Binary phase diagrams for Fe—W and Ni—W demonstrate that nickel is capable of dissolving substantially more tungsten than iron in solid state. Nickel is capable of dissolving 30 weight percent tungsten in solid phase while the solubility of tungsten in iron is limited. Further, the density of iron is lower than nickel thereby requiring more tungsten to achieve a higher density. Both of these conditions result in an iron-tungsten alloy being multiple-phase rather than a desired single phase, with an intermetallic phase that is brittle and difficult to polish. Further, a single phase is better for finishing, more malleable and has better corrosion resistance.
One specific article of manufacture is an iron-type golf club head, which are typically composed of a stainless steel or titanium material, and are typically cast or forged. Most golfers desire that their irons have a large sweet spot for greater forgiveness, a low center of gravity to get the ball in the air, a solid sound, reduced vibrations during impact, and a trim top line for appearance. Unfortunately, these desires are often in conflict with each other as it pertains to an iron.
The use of iron club heads composed of different materials has allowed some prior art irons to achieve some of these desires.
One example is U.S. Pat. No. 5,228,694 to Okumoto et al., which discloses an iron club head composed of a stainless steel sole and hosel, a core composed of a bulk molding compound or the like, a weight composed of a tungsten and polyamide resin, and an outer-shell composed of a fiber-reinforced resin.
Another example is set forth in U.S. Pat. Nos. 4,792,139, 4,798,383 and 4,884,812, all to Nagasaki et al., which disclose an iron club head composed of stainless steel with a fiber reinforced plastic back plate to allow for weight adjustment and ideal inertia moment adjustment.
Another example is U.S. Pat. No. 4,848,747 to Fujimura et al., which discloses a metal iron club head with a carbon fiber reinforced plastic back plate to increase the sweet spot. A ring is used to fix the position of the back plate.
Another example is set forth in U.S. Pat. Nos. 4,928,972 and 4,964,640 to Nakanishi et al., which disclose an iron club head composed of stainless steel with a fiber reinforcement in a rear recess to provide a dampening means for shock and vibrations, a means for increasing the inertial moment, a means for adjusting the center of gravity and a means for reinforcing the back plate.
Another example is U.S. Pat. No. 5,190,290 to Take, which discloses an iron club head with a metal body, a filling member composed of a light weight material such as a plastic, and a fiber-reinforced resin molded on the metal body and the filling member.
Another example is U.S. Pat. No. 5,411,264 to Oku, which discloses a metal body with a backwardly extended flange and an elastic fiber face plate in order to increase the moment of inertia and minimize head vibrations.
Another example is U.S. Pat. No. 5,472,201 to Aizawa et al., which discloses an iron club head with a body composed of stainless steel, a face member composed of a fiber reinforced resin and a protective layer composed of a metal, in order to provide a deep center of gravity and reduce shocks.
Another example is U.S. Pat. No. 5,326,106 to Meyer, which discloses an iron golf club head with a metal blade portion and hosel composed of a lightweight material such as a fiber reinforced resin.
Another example is U.S. Pat. No. 4,664,383 to Aizawa et al., which discloses an iron golf club head with a metal core covered with multiple layers of a reinforced synthetic resin in order to provide greater ball hitting distance.
Another example is U.S. Pat. No. 4,667,963 to Yoneyama, which discloses an iron golf club head with a metal sole and a filling member composed of a fiber reinforced resins material in order to provide greater hitting distance.
The prior art fails to disclose an iron golf club head that is composed of multiple materials, has a low center of gravity, reduced vibrations, and a greater moment of inertia.